Segment Routing Network Processing of Packets including Packets having a Multiple Segment Routing Header Packet Structure that Provides Processing and/or Memory Efficiencies

ABSTRACT

One embodiment performs segment routing network processing of packets including segment routing packets having a multiple segment routing header packet structure that provides processing and/or memory efficiencies. In one embodiment, a particular packet is received by a particular router in a network. In response to the particular router data plane ascertaining based on the particular packet a particular segment routing (SR) policy identifying one or more ordered SR identifiers, the particular router adding one or more SR headers to the particular packet resulting in the particular packet including multiple ordered SR headers instead of the particular packet having a packet structure with a single SR header, with each of the one or more SR headers including at least one segment identifier of said one or more ordered SR identifiers. The packet with the multiple ordered SR headers is sent from the particular router.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/525,439, filed Jun. 27, 2017, which is hereby incorporated byreference in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to sending of packets through apacket network, such as, but not limited to, according to segmentrouting of packets through a packet network.

BACKGROUND

The communications industry is rapidly changing to adjust to emergingtechnologies and ever increasing customer demand. This customer demandfor new applications and increased performance of existing applicationsis driving communications network and system providers to employnetworks and systems having greater speed and capacity (e.g., greaterbandwidth). In trying to achieve these goals, a common approach taken bymany communications providers is to use packet switching technology.Packets are typically forwarded in a network forwarded based one or morevalues representing network nodes or paths.

BRIEF DESCRIPTION OF THE DRAWINGS

The appended claims set forth the features of one or more embodimentswith particularity. The embodiment(s), together with its advantages, maybe understood from the following detailed description taken inconjunction with the accompanying drawings of which:

FIG. 1A illustrates a network operating according to one embodiment;

FIG. 1B illustrates a process according to one embodiment;

FIG. 2A illustrates a packet switching device according to oneembodiment;

FIG. 2B illustrates an apparatus according to one embodiment;

FIG. 3 illustrates a segment routing (SR) packet format according to oneembodiment;

FIG. 4A illustrates a segment routing (SR) packet according to oneembodiment;

FIG. 4B illustrates a segment routing (SR) packet according to oneembodiment; and

FIG. 5 illustrates a process according to one embodiment.

DESCRIPTION OF EXAMPLE EMBODIMENTS 1. Overview

Disclosed are, inter alia, methods, apparatus, computer-storage media,mechanisms, and means associated with segment routing network processingof packets including packets having a multiple segment routing headerpacket structure that provides processing and/or memory efficiencies.

In one embodiment, a particular packet is received by a particularrouter in a network. In response to the particular router data planeascertaining based on the particular packet a particular segment routing(SR) policy identifying one or more ordered SR identifiers, theparticular router adding one or more SR headers to the particular packetresulting in the particular packet including multiple ordered SR headersinstead of the particular packet having a packet structure with a singleSR header, with each of the one or more SR headers including at leastone segment identifier of said one or more ordered SR identifiers. Thepacket with the multiple ordered SR headers is sent from the particularrouter.

In one embodiment, the one or more ordered SR identifiers of theparticular SR policy includes two or more ordered segment identifiers ina particular order; and adding one or more SR headers includes addingtwo or more ordered SR headers with two or more ordered segmentidentifiers distributed among the two or more ordered SR headers suchthat each of the two or more ordered SR headers includes at least one ofthe two or more ordered segment identifiers while maintaining theparticular order for processing of the two or more ordered segmentidentifiers among and within the two or more ordered SR headers. In oneembodiment, the particular packet is received by the particular routerwithout any SR header, including without any of the ordered SR headers.

In one embodiment, the particular SR policy defines a SR path throughthe network that is associated with preferentially using multiplesmaller SR headers representing an ordered list of SR identifiers ratherthan a larger SR header representing the ordered list of SR identifiers;and wherein each said one or more SR headers is limited to a maximum ofa predetermined quantity of SR identifiers. One embodiment includes theparticular router exchanging routing information via a routing protocolwith another router in the network, which includes receiving a valuerepresenting the predetermined quantity of SR identifiers supported bythe specific router, that is SR-capable, along a path through thenetwork according to the particular SR policy, and limiting a SR headerto be processed by the specific router to having a maximum of thepredetermined quantity of SR identifiers.

2. Description

Disclosed are, inter alia, methods, apparatus, computer-storage media,mechanisms, and means associated with segment routing network processingof packets including packets having a multiple segment routing headerpacket structure that provides processing and/or memory efficiencies. Asused herein segment routing (SR) includes, but is not limited to usingInternet Protocol Version 4 or 6 (IPv4 or IPv6) addresses as segmentrouting identifiers (SIDs). Further, SR includes, but is not limitedIPv6 SR (SRv6) and/or IPv4 (SRv4).

Embodiments described herein include various elements and limitations,with no one element or limitation contemplated as being a criticalelement or limitation. Each of the claims individually recites an aspectof the embodiment in its entirety. Moreover, some embodiments describedmay include, but are not limited to, inter alia, systems, networks,integrated circuit chips, embedded processors, ASICs, methods, andcomputer-readable media containing instructions. One or multiplesystems, devices, components, etc., may comprise one or moreembodiments, which may include some elements or limitations of a claimbeing performed by the same or different systems, devices, components,etc. A processing element may be a general processor, task-specificprocessor, a core of one or more processors, or other co-located,resource-sharing implementation for performing the correspondingprocessing. The embodiments described hereinafter embody various aspectsand configurations, with the figures illustrating exemplary andnon-limiting configurations. Computer-readable media and means forperforming methods and processing block operations (e.g., a processorand memory or other apparatus configured to perform such operations) aredisclosed and are in keeping with the extensible scope of theembodiments. The term “apparatus” is used consistently herein with itscommon definition of an appliance or device.

The term “route” is used to refer to a fully or partially expandedprefix (e.g., 10.0.0.1 or 10.0.*.*), which is different than a “path”through the network which refers to a nexthop (e.g., next router) orcomplete path (e.g., traverse router A then router B, and so on). Also,the use of the term “prefix” without a qualifier herein refers to afully or partially expanded prefix.

The steps, connections, and processing of signals and informationillustrated in the figures, including, but not limited to, any block andflow diagrams and message sequence charts, may typically be performed inthe same or in a different serial or parallel ordering and/or bydifferent components and/or processes, threads, etc., and/or overdifferent connections and be combined with other functions in otherembodiments, unless this disables the embodiment or a sequence isexplicitly or implicitly required (e.g., for a sequence of read thevalue, process said read value—the value must be obtained prior toprocessing it, although some of the associated processing may beperformed prior to, concurrently with, and/or after the read operation).Also, nothing described or referenced in this document is admitted asprior art to this application unless explicitly so stated.

The term “one embodiment” is used herein to reference a particularembodiment, wherein each reference to “one embodiment” may refer to adifferent embodiment, and the use of the term repeatedly herein indescribing associated features, elements and/or limitations does notestablish a cumulative set of associated features, elements and/orlimitations that each and every embodiment must include, although anembodiment typically may include all these features, elements and/orlimitations. In addition, the terms “first,” “second,” etc., as well as“particular” and “specific” are typically used herein to denotedifferent units (e.g., a first widget or operation, a second widget oroperation, a particular widget or operation, a specific widget oroperation). The use of these terms herein does not necessarily connotean ordering such as one unit, operation or event occurring or comingbefore another or another characterization, but rather provides amechanism to distinguish between elements units. Moreover, the phrases“based on x” and “in response to x” are used to indicate a minimum setof items “x” from which something is derived or caused, wherein “x” isextensible and does not necessarily describe a complete list of items onwhich the operation is performed, etc. Additionally, the phrase “coupledto” is used to indicate some level of direct or indirect connectionbetween two elements or devices, with the coupling device or devicesmodifying or not modifying the coupled signal or communicatedinformation. Moreover, the term “or” is used herein to identify aselection of one or more, including all, of the conjunctive items.Additionally, the transitional term “comprising,” which is synonymouswith “including,” “containing,” or “characterized by,” is inclusive oropen-ended and does not exclude additional, unrecited elements or methodsteps. Finally, the term “particular machine,” when recited in a methodclaim for performing steps, refers to a particular machine within the 35USC § 101 machine statutory class.

Disclosed are, inter alia, methods, apparatus, computer-storage media,mechanisms, and means associated with segment routing network processingof packets including packets having a multiple segment routing headerpacket structure that provides processing and/or memory efficiencies. Apacket structure is a particular way of organizing information (e.g.,header and packet data) of a packet for storing, processing, andcommunicating in and among network nodes (e.g., routers, hosts).

Different packet structures have varying storage and processingrequirements. A segment routing implementation may specify that a singlesegment routing header is to be used. Further, a segment routingimplementation may specify that the ordered list of segments within asegment routing header is to be processed in order from the segmentidentifier furthest from the beginning of the packet to the one closestto beginning of the packet.

One embodiment improves the storage and processing efficiencies of a SRpacket by including multiple ordered segment routing headers with eachcontaining a small number (e.g., one, two, three, etc.) of segmentidentifiers. Thus, one embodiment might use one or more segment routingheaders rather than a single segment routing header. The packetstructure of one embodiment allows for fewer read operations (e.g.,possibly a single read operation) to access the current segment routingidentifier based on which the packet is processed. The packet structureof one embodiment allows for a smaller memory and fewer processingoperations to locate and determine the current segment routingidentifier based on which the packet is processed as the depth of thesegment list can be limited, including to the processing capabilities ofnetwork nodes through which the packet will traverse. The packetstructure of one embodiment allows for more efficient processing of apacket by having multiple segment routing headers which are added andprocessed by different administrative domains. The packet structure ofone embodiment allows for more efficient processing of a packet byadding a segment routing header rather than manipulating an existingsegment routing header, such as for, but not limited to re-routing ofthe segment routing path of a packet through the network.

FIG. 1A illustrates network 100 operating according to one embodiment.As shown, network 100 includes client networks 101 and 103 (which arethe same network in one embodiment) external to segment routing (SR)network 110, which includes SR edge nodes 111 and 113 and a network 112of network nodes including SR-capable routers (and possibly some thatare not SR-capable in that they do not process a segment routingheader/identifier), SR gateways, and service functions. In oneembodiment, SR edge nodes 111 and 113 typically encapsulate nativepackets received from networks 101 and 103 into SR packets according toa data plane ascertained SR policy, and subsequently decapsulate nativepackets from SR packets and forward the native packets into network 101and 103.

In response to receiving a packet, a SR edge node 111, 113 and/or a SRnode within network 112 determines a SR policy (e.g., list of segments)through and/or to which to forward a SR packet encapsulating the nativepacket. These policies can change in response to network conditions,network programming, etc. In one embodiment, the SR policy specifies toadd one or more SR headers, each with one or more SR identifiers,resulting in a SR packet having multiple SR headers. In one embodiment,a native packet is received without a SR header, and the SR nodeencapsulates the native packet in a SR packet including multiple addedSR headers, each including one or more SR identifiers. In oneembodiment, a SR packet is received with a SR header, and with SR nodeadding one or more SR headers resulting in a SR packet includingmultiple added SR headers, each including one or more SR identifiers. Incontrast, and for each of these scenarios a single SR header could havebeen used that includes all of the SR identifiers. However, such apacket structure does not provide the processing and/or memoryefficiencies provided by using multiple SR headers.

FIG. 1B illustrates a process according to one embodiment associatedwith distributing segment routing information in a network. Processingbegins with process block 120. In process block 122, SR routers in theSR networks continuously advertise and exchange segment routinginformation and other routing information (e.g., IPv4 or IPv6 topologyinformation) via one or more routing protocols and/or via one or morelabel distribution protocols. In one embodiment, one or more SR routersadvertise a predetermined maximum or preferred number (e.g., forincreased or maximum efficiency) of segment identifiers to include in aSR header that will be processed by the corresponding SR node. In oneembodiment, such advertising identifies those SR nodes that gainprocessing and/or memory efficiencies when a SR header when a SR headerhas only a small number of segment identifiers. In one embodiment, avalue (e.g., number, flag, range) corresponding to a predeterminedquantity is advertised. In process block 124, SR (and other) networknodes continuously update their SR policies and/or routing informationas required (e.g., based on information received via a routing protocol,from a network management system, etc.). Processing of the flow diagramof FIG. 1B is complete as indicated by process block 129.

FIGS. 2A-B and their discussion herein provide a description of variousSR network nodes according to one embodiment.

FIG. 2A illustrates one embodiment of a SR-capable packet switchingdevice 200 (e.g., SR gateway, appliance, router, packet switchingdevice, possibly with one or more service functions) according to oneembodiment. As shown, packet switching device 200 includes multiple linecards 201 and 205, each with one or more network interfaces for sendingand receiving packets over communications links (e.g., possibly part ofa link aggregation group), and with one or more processing elements thatare used in one embodiment associated with segment routing networkprocessing of packets including packets having a multiple segmentrouting header packet structure that provides processing and/or memoryefficiencies. Packet switching device 200 also has a control plane withone or more processing elements 202 for managing the control planeand/or control plane processing of packets associated with segmentrouting network processing of packets including packets having amultiple segment routing header packet structure that providesprocessing and/or memory efficiencies. Packet switching device 200 alsoincludes other cards 204 (e.g., service cards, blades) which includeprocessing elements that are used in one embodiment to process (e.g.,forward/send, drop, manipulate, change, modify, receive, create,duplicate, perform SR gateway functionality possibly with shared memorywith one or more service functions, apply a service according to one ormore service functions) packets associated with segment routing networkprocessing of packets including packets having a multiple segmentrouting header packet structure that provides processing and/or memoryefficiencies, and some hardware-based communication mechanism 203 (e.g.,bus, switching fabric, and/or matrix, etc.) for allowing its differententities 201, 202, 204 and 205 to communicate. Line cards 201 and 205typically perform the actions of being both an ingress and egress linecard, in regards to multiple other particular packets and/or packetstreams being received by, or sent from, packet switching device 200. Inone embodiment, a SR gateway and service functions are implemented on aline card 201, 205.

FIG. 2B is a block diagram of an apparatus 220 used in one embodimentassociated with segment routing network processing of packets includingpackets having a multiple segment routing header packet structure thatprovides processing and/or memory efficiencies. In one embodiment,apparatus 220 performs one or more processes, or portions thereof,corresponding to one of the flow diagrams illustrated or otherwisedescribed herein, and/or illustrated in another diagram or otherwisedescribed herein.

In one embodiment, apparatus 220 includes one or more processor(s) 221(typically with on-chip memory), memory 222 (possibly shared memory),storage device(s) 223, specialized component(s) 225 (e.g. optimizedhardware such as for performing lookup and/or packet processingoperations and/or service function, associative memory, binary and/orternary content-addressable memory, etc.), and interface(s) 227 forcommunicating information (e.g., sending and receiving packets,user-interfaces, displaying information, etc.), which are typicallycommunicatively coupled via one or more communications mechanisms 229(e.g., bus, links, switching fabric, matrix), with the communicationspaths typically tailored to meet the needs of a particular application.

Various embodiments of apparatus 220 may include more or fewer elements.The operation of apparatus 220 is typically controlled by processor(s)221 using memory 222 and storage device(s) 223 to perform one or moretasks or processes. Memory 222 is one type ofcomputer-readable/computer-storage medium, and typically comprisesrandom access memory (RAM), read only memory (ROM), flash memory,integrated circuits, and/or other memory components. Memory 222typically stores computer-executable instructions to be executed byprocessor(s) 221 and/or data which is manipulated by processor(s) 221for implementing functionality in accordance with an embodiment. Storagedevice(s) 223 are another type of computer-readable medium, andtypically comprise solid state storage media, disk drives, diskettes,networked services, tape drives, and other storage devices. Storagedevice(s) 223 typically store computer-executable instructions to beexecuted by processor(s) 221 and/or data which is manipulated byprocessor(s) 221 for implementing functionality in accordance with anembodiment.

FIG. 3 illustrates a segment routing packet structure 300 according toone embodiment. As shown, SR packet structure 300 includes an IP header301 (e.g., IPv6, IPv4), multiple ordered segment routing headers 310,and the native (encapsulated) packet 321. Each of multiple ordered SRheaders 310 (which includes SR headers 311-319) typically includes oneor more SR identifiers. By allowing multiple, typically smaller SRheaders, SR packet format 300 provides processing and/or memoryefficiencies especially for limited-capability (e.g., less memory, lessprocessing power) SR routers.

As shown, multiple ordered SR headers 310 includes one to n SR headers311-319, with n being a positive integer. Each of these ordered SRheaders 311-319 includes an ordered list of one or more segmentidentifiers (e.g., IPv6 or IPv4 address), each representing a segment(e.g., locator, function, argument) in the network used to process(e.g., forward, manipulate, modify) a SR packet in and through a SRnetwork.

FIG. 4A illustrates a segment routing (SR) packet 400 encapsulating anative packet 421 according to one embodiment. As shown, SR packet 400includes an IP header 401 and two ordered SR headers 410. SR headers 411and 412 are processed in order with SR header-1 (411) is processedfirst, then SR header-2 (412) is processed. The processing of SRidentifiers within SR header-1 (411) is performed in order that being Athen B. Similarly, processing of SR identifiers within SR header-2 (412)is performed in order that being C, then D, then E. In one embodiment,when all SR identifiers have been processed in a SR header, the SRheader is removed. In one embodiment, when all SR identifiers have beenprocessed in a SR header, then a current SR header is advanced so that anext SR header is processed.

FIG. 4B illustrates a segment routing (SR) packet 430 encapsulating anative packet 421 according to one embodiment. As shown, SR packet 430includes an IP header 431 a single SR header 441, which includes allfive of the SR identifiers 441 shown in FIG. 4A and distributed acrossmultiple SR headers 410 therein.

The network processing (e.g., forwarding, manipulating, modifying) ofthe encapsulated native packet 421 in SR packet 430 (FIG. 4B) and in SRpacket 400 (FIG. 4A) is effectively the same, as the same set of SRidentifiers will be processed in the same order. However, the packetstructure of SR packet 400 (FIG. 4A) provides some processing and memoryefficiencies in one embodiment.

FIG. 5 illustrates a process according to one embodiment. Processingbegins with process block 500. In process block 502, a packet isreceived. In process block 504, data plane processing ascertains (e.g.,acquires from memory based on the received packet, such as by, but notlimited to, based on a destination address or current segment identifierof the received packet).

As determined in process block 505, if the packet was received with a SRheader, then processing proceeds to process block 506; otherwise,processing proceeds to process block 511. Continuing with process block506, the SR header of the received packet is updated to a next currentSR identifier (possibly removing a completely processed SR header)and/or decapsulating an encapsulated packet, with processing proceedingto process block 511. In one embodiment, the processing of process block506 is performed later in the processing of the flow diagram of FIG. 5,possibly performed in conjunction with other updates to the receivedpacket for efficiency.

Continuing with, and as determined in process block 511, if the SRpolicy identifies to add a SR header to the received packet, thenprocessing proceeds to process block 514; otherwise, processing proceedsto process block 512 wherein the packet is processed normally andprocessing proceeds to process block 519.

Continuing with process block 514 and according to the SR policy, a SRpacket is created or an additional SR header is added to the receivedpacket resulting in a SR packet including multiple ordered SR headers(e.g., one, two, three SR headers), each with one or more SRidentifiers. In one embodiment, two SR headers are added instead of asingle SR header. In one embodiment, an additional SR header is added tothe received SR packet instead of adding corresponding SR identifiers tothe existing SR header. Next, in process block 516, the packet isforwarded (e.g., sent according to routing information) from the SRnode, and processing continues with process block 519.

Continuing with process block 519, processing of the flow diagram ofFIG. 5 is complete.

In view of the many possible embodiments to which the principles of thedisclosure may be applied, it will be appreciated that the embodimentsand aspects thereof described herein with respect to thedrawings/figures are only illustrative and should not be taken aslimiting the scope of the disclosure. For example, and as would beapparent to one skilled in the art, many of the process block operationscan be re-ordered to be performed before, after, or substantiallyconcurrent with other operations. Also, many different forms of datastructures could be used in various embodiments. The disclosure asdescribed herein contemplates all such embodiments as may come withinthe scope of the following claims and equivalents thereof.

What is claimed is:
 1. A method, comprising: receiving a particularpacket by a particular router in a network; in response to theparticular router data plane ascertaining based on the particular packeta particular segment routing (SR) policy identifying one or more orderedSR identifiers, the particular router adding one or more SR headers tothe particular packet resulting in the particular packet including aplurality of ordered SR headers instead of the particular packet havinga packet structure with a single SR header, with each of said one ormore SR headers including at least one segment identifier of said one ormore ordered SR identifiers; and sending the packet with the pluralityof ordered SR headers from the particular router.
 2. The method of claim1, wherein said one or more ordered SR identifiers of the particular SRpolicy includes two or more ordered segment identifiers in a particularorder; and said adding one or more SR headers includes adding two ormore ordered SR headers with said two or more ordered segmentidentifiers distributed among said two or more ordered SR headers suchthat each of said two or more ordered SR headers includes at least oneof said two or more ordered segment identifiers while maintaining theparticular order for processing of said two or more ordered segmentidentifiers among and within said two or more ordered SR headers.
 3. Themethod of claim 2, wherein the particular packet is said received by theparticular router without any SR header, including without any of theplurality of ordered SR headers.
 4. The method of claim 2, wherein saidtwo or more ordered segment identifiers includes at least three segmentidentifiers.
 5. The method of claim 2, wherein each of said two or moreSR headers comprises either one or more Internet Protocol Version 6(IPv6) Segment Identifiers (SRv6 SIDs) of said one or more ordered SRidentifiers or one or more Internet Protocol Version 4 (IPv4) segmentidentifiers of said one or more ordered SR identifiers but does notcomprise both IPv4 and IPv6 segment identifiers; and wherein said two ormore ordered SR identifiers includes an IPv4 segment identifier and anIPv6 SID.
 6. The method of claim 5, wherein all of said one or moreordered SR identifiers are an IPv6 Segment Identifiers (SIDs).
 7. Themethod of claim 2, comprising the particular router limiting each ofsaid two or more SR headers to less than or equal to two SR identifiers.8. The method of claim 1, wherein the particular packet when saidreceived by the particular router already includes one of the pluralityof ordered SR headers.
 9. The method of claim 1, comprising theparticular router limiting each of said one or more SR headers to lessthan or equal to two SR identifiers.
 10. The method of claim 1, whereinsaid one or more ordered SR identifiers of the particular SR policyincludes an Internet Protocol Version 4 (IPv4) segment identifier. 11.The method of claim 10, wherein said one or more ordered SR identifiersof the particular SR policy includes an Internet Protocol Version 6(IPv6) segment identifier.
 12. The method of claim 1, wherein theparticular SR policy defines a SR path through the network that isassociated with preferentially using multiple smaller SR headersrepresenting an ordered list of SR identifiers rather than a larger SRheader representing the ordered list of SR identifiers; and wherein eachsaid one or more SR headers is limited to a maximum of a predeterminedquantity of SR identifiers.
 13. The method of claim 1, comprising theparticular router exchanging routing information via a routing protocolwith another router in the network, which includes receiving a valuerepresenting the predetermined quantity of SR identifiers supported bythe specific router, that is SR-capable, along a path through thenetwork according to the particular SR policy, and limiting a SR headerto be processed by the specific router to having a maximum of thepredetermined quantity of SR identifiers.
 14. The method of claim 1,wherein the particular segment routing (SR) policy designates a specificSR identifier corresponding to a specific router, that is SR-capable, inthe network; wherein the method includes the particular routerexchanging routing information via a routing protocol with anotherrouter in the network, which includes receiving an advertisementassociated with the specific router and including a value representing apredetermined quantity of SR identifiers; and wherein a specific SRheader of said one or more SR headers that includes the specific SRidentifier is limited to a maximum of the predetermined quantity of SRidentifiers in response to said advertisement.
 15. The method of claim14, comprising: receiving the particular packet by the specific routerin the network subsequent to said sending by the particular router; anddata plane processing of the particular packet based on the specific SRidentifier.
 16. A method, comprising: receiving a particular packet by aspecific router in a network, with the particular packet including aplurality of ordered segment routing (SR) headers instead of theparticular packet having a packet structure with a single SR header,with each of the plurality of ordered SR headers including at least onesegment identifier of a plurality of ordered SR identifiers, and with aspecific SR identifier associated with the specific router in thedestination address in the Internet Protocol Version 4 or 6 header ofthe particular packet; and data plane processing, by the specificrouter, of the particular packet based on the specific SR identifier.17. The method of claim 16, including the specific router advertising,via a routing protocol with another router in the network, the specificSR identifier associated with a value representing a predeterminedquantity of SR identifiers; wherein a current SR header of the pluralityof ordered SR headers includes a maximum of the predetermined quantityof SR identifiers as said advertised.
 18. The method of claim 16,wherein each of the plurality of ordered SR headers comprises either oneor more Internet Protocol Version 6 (IPv6) Segment Identifiers (SRv6SIDs) of said one or more ordered SR identifiers or one or more InternetProtocol Version 4 (IPv4) segment identifiers of said one or moreordered SR identifiers but does not comprise both IPv4 and IPv6 segmentidentifiers; and wherein the plurality of ordered SR identifiersincludes an IPv4 segment identifier and an IPv6 SID.
 19. An apparatus,comprising: one or more hardware interfaces sending and receivingpackets; and one or more network processors with memory associatedtherewith; wherein the apparatus, communicatively coupled in a network,performs packet processing operations including segment routing-capable(SR-capable) packet processing operations, with said packet processingoperations including: receiving on an interface of said one or morehardware interfaces a particular packet; in response to data planeascertaining based on the particular packet a particular segment routing(SR) policy identifying one or more ordered SR identifiers, adding oneor more SR headers to the particular packet resulting in the particularpacket including a plurality of ordered SR headers instead of theparticular packet having a packet structure with a single SR header,with each of said one or more SR headers including at least one segmentidentifier of said one or more ordered SR identifiers; and sending thepacket with the plurality of ordered SR headers from the apparatus on aninterface of said one or more hardware interfaces.
 20. The apparatus ofclaim 19, wherein said one or more ordered SR identifiers of theparticular SR policy includes two or more ordered segment identifiers ina particular order; and said adding one or more SR headers includesadding two or more ordered SR headers with said two or more orderedsegment identifiers distributed among said two or more ordered SRheaders such that each of said two or more ordered SR headers includesat least one of said two or more ordered segment identifiers whilemaintaining the particular order for processing of said two or moreordered segment identifiers among and within said two or more ordered SRheaders.